Temperature- and Time-Dependent Stereochemical Control in Thermally Induced Keto−Ene Cyclizations
作者:Rafael Pedrosa、Celia Andrés、Carlos D. Rosón、Martina Vicente
DOI:10.1021/jo026525m
日期:2003.3.1
Reaction conditions determine the stereoselection in the intramolecular keto-ene reaction. The thermolysis of chiral 2-acyl-3-allyl-substituted 1,3-perhydrobenzoxazines derivedfrom (-)-8-aminomenthol gives a mixture of only two cis-3-hydroxy-3,4-disubstituted pyrrolidine nuclei. The stereochemistry of the major diastereoisomer depends on both the temperature and the reaction time.
Diastereoselective Synthesis of Enantiopure Morpholines by Electrophilic Selenium-Induced 6-<i>e</i><i>xo </i>Cyclizations on Chiral 3-Allyl-2-hydroxymethylperhydro-1,3-benzoxazine Derivatives
chiral 3-allyl-2-hydroxymethyl-substituted perhydro-1,3-benzoxazine derivatives. The cyclization occurs in high yields and diastereoselection, although the temperature of the reaction and the structure of the substituent at C-2 and the substitutionpattern of the double bond can modify the regio- and stereochemistry of the final products.
Lewis acid mediated diastereoselective keto-ene cyclization on chiral perhydro-1,3-benzoxazines: synthesis of enantiopure cis-3,4-disubstituted 3-hydroxypyrrolidines
作者:Celia Andrés、Israel González、Javier Nieto、Carlos D. Rosón
DOI:10.1016/j.tet.2009.09.091
日期:2009.11
Chiral 2-acyl-3-allyl-perhydro-1,3-benzoxazines derived from (-)-8-aminomenthol were easily cyclized in the presence of Lewis acids at 0 degrees C. The diastereoselectivity of the cyclization was dependent on the nature of the Lewis acid. The cyclization compounds can be transformed into enantiopure cis-3,4-disubstituted 3-hydroxypyrrolidines by ring opening of the N,O-acetal moiety and subsequent elimination of the menthol appendage. (C) 2009 Elsevier Ltd. All rights reserved.